The subject matter described herein relates generally to methods and systems for the pressure measurement on airfoils and hydrofoils, and more particularly, to methods and systems for the pressure measurement on wind turbine rotor blades.
At least some known wind turbines include a tower and a nacelle mounted on the tower. A rotor is rotatably mounted to the nacelle and is coupled to a generator by a shaft. A plurality of blades extend from the rotor. The blades are oriented such that wind passing over the blades turns the rotor and rotates the shaft, thereby driving the generator to generate electricity.
In order to optimize the aerodynamic properties of airfoils, hydrofoils, and particularly of wind turbine rotor blades, the pressure distribution around the profile of the same may be measured. For this purpose, a number of techniques are well known. Amongst others, it is known to drill small holes into the surface of the structure and to apply pressure tubes which are routed to a measurement system inside the structure. Further, the application of pitot tubes or pressure sensors on the surface of the profile of a foil or wing is also applied. If the pressure close to the surface of the structure shall be measured, pressure sensors are typically mounted in small holes in the surface, which allows for a measurement at face level.
However, this involves a number of disadvantages. The surface of the rotor blade or airfoil is typically manipulated by drilling holes in which the sensors are placed. Though sensors may also be mounted to the aerodynamic face of the structure, e.g. via the use of adhesives, this can lead to an undesirable distortion of the airflow in the vicinity of the attached sensor and thus to biased or misleading measurement results. Further, for acquiring the measurement data, wires have to be installed. These are typically routed through the interior of the blade or wing, involving a significant amount of labor, which is time consuming and at least partially leads to changes in the structure of the blade or wing. Sometimes, it may also be difficult or impossible to route wires through a structure because of its structural properties or accessibility. The wires may also be installed on the surface of an airfoil or rotor blade, which requires less time and effort, but may contribute to a distortion of the airflow in the vicinity of the sensors, and thus to a degradation of the quality of the acquired data.
In view of the above, it is desirable to have a technique which allows for the measurement of pressures and pressure gradients close to the surface of an airfoil or hydrofoil, and more particularly of a wind turbine component, and which avoids the above cited disadvantages.